Crank counterbalance



Jan. 26, 1937. c. M. FERGUSSON 2,069,031 CRANK COUNTERBALANCE I Oi'iginaI Filed June 21,, 1932 2 Sheets-Sheet 1 /v 1 2/ /Th 20 57 v 1 I .2 s

r 1 5 -1 H. 1 I v 62405 M Fem/s50 Jan. 26, 1937. c. M. FERGUSS ON 3 CRANKCOUNTERBALANCE' Original Filed June 21, 1932 2 Sheets-Sheet 2 v F i mm inning-4 J 52% 4, Owl/w M 55/850550.

Patented Jan. 26, 1937 UNITED STATES PATENT OFFICE Application June 21, 1932, Serial No. 618,543

Renewed October 12, 1933 9 Claims.

The invention relates to counterbalances intended primarily for use with standard pump rigs.

It has been recognized that in pumping deep wells for oil, water and the like, it is desirable to counterbalance the weight of the pump rods, pistons and other moving parts of the apparatus, and to this end various forms of counterbalances have been employed, the most successful types of which are applied to the rotating crank arm which forms a part of the standard rig. While this type of device aids to a large degree in 'counterbalancing the weight of the moving parts, and assists in raising the Weight of the load, and in avoiding to some extent the jerk or strain exerted by the load upon the rods on the down stroke, I have found that even with the use of such counterbalances there is considerable jerk or strain upon the pump rods owing to the fact that the counterbalancing effect is not properly applied.

It will be apparent that the load on the up stroke of the piston, at which time oil is being lifted, is greater than on the down stroke, after a considerable quantity of the oil has been discharged. Moreover, in deep wells such as are present in many oil fields the pump rod stretches to a considerable extent on the application of power thereto before the load will be lifted, the stretch being on the average about 17 inches for a well 3000 feet deep.

In counterbalances heretofore used, these factors have not been taken into consideration, and it is largely for this reason that breakages of equipment occur so frequently.

It is accordingly one of the objects of the present invention to provide a counterbalance which will apply force in the proper amount in timed relation tothe particular cycle of operation of the pump plunger.

A further object means whereby the ily removed from the crank arm readily reapplied.

' Other objects of the invention will be apparent from a consideration of the accompanying drawings and the following detailed description of a preferred embodiment of the invention.

In the drawings,

Fig. 1 is a side elevation of a pumping unit equipped with the improved counterbalance, a portion of the interior of the well being shown in section;

Fig. 2 is an elevation on an enlarged scale of the invention is to provide counterbalance may be readof the rig and well I I, provided with tubing 12 in which a pump plunger l3 reciprocates in the usual manner. Numeral M denotes the usual valve located below the plunger. The pump rod is reciprocated by means of a walking beam 15 pivoted intermediate its ends to Sampson post I6. To the opposite end of the walking beam there is attached the usual pitman H, which is secured to a crank arm l8 by means of a wrist pin [9, which extends through one of a plurality of holes in the crank arm 18. The desired adjustment may be secured by inserting the wrist pin in the proper hole, this being dependent on the depth of the well and the weight of the pump rod. The crank arm 18, as shown, is mounted at the end of a shaft 2| which is suitably supported by jack posts, one of which is indicated at 22. The shaft may be rotated in the usual manner by means of a band wheel 23.

It will be understood that the above elements are conventional parts of the standard rig and form no part of the present invention. Other forms of pumping rig may be employed without departing from my invention.

According to the present embodiment of my invention, the shaft 2| extends through a drum 24 which is rigidly carried by a suitable support 25, herein shown as attached to the jack post 22. It will be noted that the drum is eccentric with reference to the shaft 2| and is provided with flanges and an intermediate groove. A yoke 26 composed of two parts is secured about the drum in the groove thereof, the parts of the yoke being secured at the top by means of a bolt 21 and adjustably connected at the lower portion by means of bolts 28 which hold the parts of the yoke together and attach the yoke to a connecting rod 20. It will be obvious that the drum may be made in separate parts, permitting the front flange to be removed and a one-piece yoke applied thereto, instead of employing a two-piece yoke as herein described. The connecting rod 29 is attached at its lower end to a pin 30 which extends through an opening 3| in a main counterweight member 32. This counterweight is composed of metal and, while its weight may on the average about differ for various wells, it will preferably weigh 4000 pounds. It will be understood that this weight is given, not by way of limitation, but merely by way of explanation. The counterweight 32 may be provided with re movable sections 33, so that its weight may be varied according to the exigencies of the particular case.

As shown most clearly in Fig. 5, the counterweight 32 is provided with a cut-away portion 34 substantially rectangular in shape, the vertical edges of which are curved or V-shaped to provide guides for an auxiliary counterweight member to be described hereinafter. Holes 36 extend from the bottom of the cut-away portion entirely through the counterweight and are adapted to receive guide pins 37 carried by a separate member 38 having curved edges to cooperate with the grooved guides 35 in the main counterweight 32. The auxiliary counterweight 38 is substantially rectangular in form, but is of less height than the rectangular opening 34 in the main counterweight.

As shown, the auxiliary counterweight is notched in its upper surface at 39 to provide a keyway, and is provided with threaded sockets 40, 40, located one on each side of the keyway. The crank arm i8 is provided with Wings 4!, 4i, and a key member 42, which is adapted to engage within the keyway 39 formed in the auxiliary counterweight member. The wings 4|, 4| are provided with holes 43, 43 through which are passed bolts 44, 44, which are screwed into the sockets 40, 40 and hold the auxiliary counterweight member 38 firmly against the crank arm I8.

Operation In the operation of the device it will be assumed that the band wheel 23 is rotating in a clockwise direction, as indicated by the arrow, causing a rotation in the same direction of the crank shaft 2|, crank arm 48 and counterweights 38 and 32, the latter causing rotation of the connecting rod 29 and the ecoentrically mounted yoke 26. It will be apparent that, owing to this eccentric mounting, the main counterweight member 32 will be reciprocated with reference to' the crank shaft during the rotation thereof, its distance from the crank shaft reaching a maximum when the crank arm is in horizontal position and extends to the right of the crank shaft, and being at a minimum distance when the crank arm extends horizontally to the left. These maximum and minimum positions are indicated in full and dotted lines respectively in Fig. 2. Intermediate these two extreme positions it will be obvious that the counterbalance gradually approaches and recedes from the crank shaft. During the rotation of the crank shaft the walking beam I5 is reciprocated together with the pump rod I 0 and plunger is.

Assuming the counterweight to be in the full line position shown in Figs. 1 and 2, it will be obvious that the counterbalance is exerting its maximum eifect, being farthest from the shaft 2| about which it rotates. At this position the peak load has been reached by the pump, the plunger E3 of which is rising, carrying with it a column of liquid. As the shaft continues to rotate, the counterbalance recedes from its maximum position and the pump plunger is approaching the top of its stroke. In the dotted line position shown in Figs. 1 and 2, the crank arm extends vertically downward and the liquid is being delivered at the top of the plunger stroke.

After the liquid has been delivered, the pump rod and plunger start downward and the counterbalance starts upward. Since the liquid load no longer requires compensation, a smaller counterbalancing effect is desirable, and consequently the counterbalance is closer to the shaft during the down stroke of the piston rod than during the up stroke. When the counterbalance has reached the dotted line position shown at the left in Fig. 2, its counterbalancing effect is at a minimum. After passing this position the load on the motor becomes less and there is a tendency to speed up the machinery. This effect is overcome by the compensating action of the counterbalance, which gradually recedes from the crank shaft as the counterbalance approaches the uppermost position.

When the counterbalance is in its uppermost position, the pump plunger is in its lowest position, and is just ready for the up stroke to commence. As the counterbalance leaves the uppermost position, the first effect is to stretch the plunger rod, after which the plunger commences to rise, carrying with it its load of liquid. As the counterbalance again approaches the full line position shown in Figs. 1 and 2, the peak load is approached and the counterbalance continues to recede from the crank shaft, increasing the lifting effect of the counterbalance.

It will be seen from the above description that, owing to the compensating action of the counterbalance, uniformity of speed is maintained throughout the stroke, thus eliminating stress in the piston rod and avoiding consequent breakage. v 7

It is frequently necessary to remove the counterweight from the crank arm in order to permit cleaning of the well, repair of the pump rod and other necessary operations. The present device is designed to permit this necessary operation with a. minimum of effort. All that is necessary is to place blocks or logs beneath the main counterweight 32, such logs being indicated at in Fig. 6. The bolts 43 which hold the auxiliary counterweight 38 are now unscrewed suinciently to allow the auxiliary counterweight to drop until the top of the keyway 39 clears the bottom of the key 42 carried by the crank arm l8. This position is indicated in Fig. 6. A block of wood or the like 46 may then be inserted between the auxiliary counterweight and the main counterweight, whereupon the bolts 43 will be entirely removed, permitting the crank arm l8 to rotate freely without afiecting the counterweights. To reapply the counterweights the bolts are replaced and tightened, thereby raising the auxiliary counterweight and permitting removal of the block 46. The blocks 45 beneath the main counterweight are also removed and the device is ready for normal operation. Since in the average device the auxiliary counterweight 38 will have a weight not exceeding 200 pounds, whereas the main counterweight may weigh 4000 pounds or more, the saving in effort will be apparent. Moreover, the bolts 43 serve as a convenient means for raising and lowering the auxiliary counterweight and these can be readily operated by one man. The word eccentric as used in the claims is not necessarily limited to a disk of circular form, since it is obvious that any form may be used, provided it is eccentric to the shaft. Any suitable connection may be made between such eccentric and the weight.

One embodiment of the invention has been described in detail for the purpose of illustration, but it will be understood that the invention is not limited to such details, and that many modifications which will be apparent to one skilled in the art may be resorted to without departing from the spirit of my invention.

It will be obvious that the reciprocating operation of the improved counterbalance will result in considerable saving of power, over the noncompensating form of counterbalance, the extent of which will be governed only by the amount of compensation mechanically desirable, and should not be less than 25% in any case. Experience has shown that the pumping problems of no two wells are the same, so that details of the device may be varied according to the requirements of the particular case without departing from the spirit of the invention.

What I claim is:

1. In combination with a crank shaft having a weighted crank arm, a stationary drum eccentrically mounted with reference to the crank shaft, a yoke about said drum, a connecting rod carried by the yoke, a counterweight member attached to said connecting rod, and connections whereby said counterweight is rotated by said crank arm and reciprocated with reference to the crank shaft during rotation thereof.

2. In combination with a rotating shaft, a counterweight, connections between said shaft and counterweight for rotating the latter, and means for reciprocating said counterweight member with reference to the shaft during rotation thereof, said means including a fixed drum mounted eccentrically with reference to the shaft and a yoke surrounding said drum and connected with the counterweight.

3. In combination with a rotatable crank shaft, a crank arm secured to the shaft, a relatively small counterweight member detachably secured thereto, a main counterweight member, means for slidably connecting said counterweight members to each other, and means independent of the crank shaft for retaining the main counterweight member in sliding connection with the small counterweight member during rotation thereof.

4. In a device of the character described, a twopart counterweight, comprising a main counterweight member having a recess extending inward from one side only, and an auxiliary counterweight mounted in said recess to slide toward and away from its bottom wall, whereby when the main member is supported with its recessed side up, the auxiliary weight may be supported on the said bottom wall.

5. In a device of the character described, a shaft, a two-part counterweight, comprising a main counterweight member having a recess in one side, and an auxiliary counterweight mounted to slide towards and from the bottom of said recess, means for rotating the counterweights on rotation of said shaft, and means for reciprocating the main counterweight with reference to the auxiliary counterweight during such rotation.

6. In a device of the character described, a rotatable crank arm, a small counterweight member detachably connected at the end of the crank arm, a large counterweight member reciprocable with reference to the small counterweight and having a recess of sufficient size to receive the small counterweight within the large counterweight, and means for supporting the large counterweight independently of the small counterweight and crank arm, whereby when the small counterweight is released from the crank arm said arm is free to rotate without aifecting the large counterweight.

'7. In a device of the character described, a shaft mounted for rotation, a weight, means for mounting said weight on the shaft for movement toward the shaft and away from it, a link pivoted at one end on a fixed pivot eccentric to the shaft, and connections between the weight and the other end of the link.

8. In a device of the character described, a crank shaft, a weighted crank arm rotated by said crank shaft, a counterweight slidingly mounted with reference to said crank arm and being rotated thereby, means for reciprocating said counterweight relative to the crank arm during rotation thereof, comprising a strap connected at one end to said counterweight and at its other end to an eccentric drum, and means for holding said eccentric against rotation.

9. In a device of the character described, a shaft mounted for rotation, a weight, means for mounting said weight on the shaft for movement toward the shaft and away from it, a link having one end on a pivot held against rotation and eccentric to the shaft, and connections between the weight and the other end of the link.

CHARLES M. FERGUSSON. 

